Neural circuits used in sensory processing must be stable enough to mediate survival-critical behaviors, and yet plastic enough to adapt to a dynamic environment. While great progress has been made in understanding how single synapses adjust response strength, less is known about the mechanisms of circuit-level development and plasticity. In the proposed study, I will use electrophysiology to investigate the connections between the two hemispheres of the Xenopus optic tectum, and their role in circuit plasticity and maturation, both in the course of normal development and in response to injury. These connections are poorly understood, and their contribution to circuit development and plasticity is unknown. The optic tectum is homologous to the mammalian superior colliculus and is critical for processing sensory information from multiple modalities. These intertectal inputs are tectal neurons which extend axons across the commissure to synapse onto tectal neurons in the contralateral hemisphere. In the superior colliculus, it has been proposed that these inputs mediate reciprocal inhibition; however the cellular and circuit-level mechanisms underlying this function are unknown. We have developed a new dissection prep in order to allow us to specifically explore 1) how intertectal inputs develop in Xenopus and how these inputs contribute to circuit formation, 2) how changes in the strength of intertectal input affects retinotectal circuit formation and plasticity and, 3) the remodeling of these inputs, and their contribution to recovery post-injury. These experiments will not only address fundamental questions of how neural circuits are formed and maintained, but will provide crucial information on changes that occur in disease states wherein synaptic connectivity is disrupted, such as schizophrenia, stroke, and traumatic brain injury.